a) Field of the Invention
The present invention concerns a process for producing a silicon containing deposit at a surface of a metallic substrate, a process for providing an anti-corrosive treatment to such a metallic substrate, and a metallized polymer support including a silicon containing deposit.
b) Description of Prior Art
It is known that metallic substrate, for example metallic sheets or strips of small thicknesses are often sensitive to corrosion, which may be induced by water or water vapor.
A number of processes have already been designed in order to decrease these risks; of corrosion. Thus, it has already been proposed to deposit silicon at the surface of these substrates, silicon having properties defining a barrier against water vapor. Moreover, a deposit of silicon enables to improve the properties of adhesion and wettability of these substrates. The processes used to achieve this rely on plasma or pyrolytic techniques. However, the plasma techniques used to this date require the use of low or very low pressures resulting in prohibitive costs. Moreover, the deposit of silicon may only be carried out on small surfaces, of the order of 100 cm.sup.2 (10.times.10 cm.sup.2). This technique is therefore not adapted for substrates with very large surfaces, such as sheets. A similar problem is also present for the treatment of metallized polymer films having large surfaces. These films are for example intended for the manufacture of electrical condensers and are used in field of packaging. They are made of a polymer film such as a polyolefin or a polyester in which the surface is metallized with a metallic film or deposit which consists of a pure or alloyed metal, and in which the thickness is very small, generally lower than 25 nanometers.
In view of their small thicknesses, these films are very sensitive to corrosion, because the metallic part may be substantially removed after a few hours of contact with water vapor.
The pyrolytic techniques mentioned above, require the use of elevated temperatures. If such temperatures may in certain cases be acceptable for metallic sheets, they are however much higher than the melting temperatures of the polymers which constitute said metallic films.
The pyrolytic techniques are therefore completely useless for treating these films.
It is therefore a main object of the present invention to provide a process which can to produce a silicon containing deposit at the surface of a metallic substrates in order to improve for example its corrosion resistance, and its adhesion and wettability properties. This process makes it possible to obtain a deposit on substrates having large surfaces. It does not require the use of low pressure or high temperatures, which are not compatible with substrates of the metallized polymer film type.